Method of making bearings



Patented, Oct. 21, 1941 UNITED STATES PATENT OFFICE 2,250,247 METHOD orMAKING BEARINGS Ernest R. Darby and Carlos-M. Heath, Detroit, Mich.,assig'nors to Federal-Mogul Corporation, Detroit, Mich., a corporationof Michigan Application December 29, 1939, Serial No. 311,525

4Claims.

where the lining is applied in the form of metal 5 powder. The use of abronze liner in a steel back as a bearing *is not new. The lining bronzehas been made of various alloys. One such alloy or class of alloys iscopper and lead with the lead content ranging from to 45%. Another alloyis composed of copper and lead with a small percentage of tin. Anotheralloy is one of copper and lead with a small amount of nickel. Smallamounts of, silver have been used along with If) copper and lead.

Bearings with liners of these alloys, as well as others having a copperbase, have been made by diflerent methods. One method comprises the 1pouring of the melted copper base alloy into a heated steel shell in asuitable mold followed by rapid chilling. whereby the alloy is bonded orfused to the steel. Another method comprises the spinning of the meltedbearing alloy in the heated shell followed by rapid cooling. Stillanother method has been used where the bronze or. copper-lead bearingmetal is melted in a closed tube or shell in a reducing atmosphere andthe whole rotated to spin the bearing alloy into position. I

Metal powder has been used in the application of the bearing liner tothe steel supporting back of the bearing. One method makes use of apowder composed of particles of lead enveloped in a shell of copper.powder is compressed upon a steel bearing back which has beenelectroplated or otherwise coated with a thin layer of copper. Thepowder layer is sintered into position under pressure at relatively hightemperature, thereby bonding the particles 4 of powder together and thelayer as a whole to the copper plated steel back. Another method employsa mechanical mixture of copper and lead powder or of copper, lead andtin powders. The

powder mixture is compressed upon a steel backing which has been coatedwith a thin lead-tin layer. A very high pressure is used whereby thecompressed powder layer imbeds in the lead-tin layer suillcientiy to beheld in place during handling and sinterlng. Sintering under pressure ata temperature around 1500 F, afl'ects bonding of the bearing layer tothe steel and a union of the metal particles in the bearing layer. Othermethods similar in nature have been used and powders of variouscompositions have been This copper coated lead 35 employed. Onecomposition contains graphite particles along with the copper, tin andlead, and a chemical is frequently added for the purpose oi producingporositywhich later is supposed to absorb lubricating oil. p

All of the bronze or copper-lead lined bearings as herebefore describedhave characteristics which are more or less undesirable either from amanufacturing standpoint or in actual bearing service. It has been foundby experimental tests that the iron which is dissolved into the bronteor the copper-lead when the melted alloy is poured into a steel bearingshell, lowers the bearing properties of the finished bearing. Otherimpurities dissolve in the bearing alloy during the melting process, andwith some melting units and processes it is necessary to add' metallicor nonmetalllc elements or substances known as fluxes to remove gas oroxide and in other manners improve the castability of the melted metal.These fluxes, if allowed to remain in the alloy, are in some instancesharmful to bearing performance.

- The high temperature employed when the melted bearing alloy is cast orspun into position on the steel backing material, necessitatesoperations which are expensive and, in addition, considerpowder upon thesteel bearing member followed by sintering under pressure, severalserious manufacturing diiiiculties are encountered. If the powder usedbe copper coated lead powder and the sintering temperature employed below enough to prevent lead sweating under pressure, the time necessaryto properly bond the particles of powder together and the whole bearinglayer to the steel backing-is very long and the operation becomesexpensive. This is also true when the powder used is a mechanicalmixture of copper and lead or of copper, lead and tin, and in this caseit is impossible with very high lead mixtures to sinter under pressurewithout sweating a large amount of lead. If sintering is attemptedwithout pressure being applied at the same time, blistering willoccur-resulting in excessive porosity and very poor bond or unionbetween the bearing metal layers and the steel back.

We have found that a satisfactory and superior bearing can be made withthe use of metal powder whereby the dimculties encountered in othermethods are eliminated. In our process we may employ either coppercoated lead powder or a mechanical mixture of copperand lead powders orcopper. tin and lead powders. In addition, we may use a mixture ofcopper coated lead powder and copper or lead powder added for thepurpose of controlling the chemical composition. We have also foundthatsmall amounts of tin may be added which, under certain conditions.is advantageous to our process.

The accompanying drawing illustrates dia-' grammatically the steps inthe preferred form of our method. In this drawing: a

Figure 1 is a section through a portion of an unplatedmetal backing forthe bearing produced by our method. I

Figure 2 shows .the backing plated with a coating of bonding material.

Figure 3 shows the powdered bearing material applied to the platedbearing backing.

tion.

Figure 5 illustrates a rolling operation which may be performed afterthe first sintering operation.

" Figure 6 is a view similar to Figure 4 illus- :trating the secondsintering operation.

. Figure 7 illustrates another rolling operationbearing blank issintered in a suitable atmosphere to prevent oiddation, at a temperatureof about 11-00 F., as indicated in Figure 4. The time of sintering willvary with the thickness of the layer of powder and the thickness of thesteel backing member. However, under average con- Figure 4 illustratesthe first sintering opera- A yer 3 F re 3) of the metal.

ditions, this time should not exceed thirty'minutes. After the bearingblank has been sintered,

it is cooled to room temperature while still main-" taining' a reducingatmosphere, and 'removed It is then put in a suitable from the furnace.I die and pressed or rolled between suitable rollers, as indicated inFigure 5, under a pressure be:-

tween 2500 and 20,000 lbs. per sq. in. depending upon the nature of thepowder-and the thickness of the layer. This pressing-operation serves tocompact the metal powder layer without danger of causing blistering orsweating in the sintering operation which is to follow. The bearingblank is then again sintered,as shown in Figure 6, for

exceeding 1700 F. Cooling is effected as before in the reducingatmosphere.

"By the above operation we have provided a bearing blank upon which thecopper-1ead*- or bronze layer is securely bonded without danger of leadsweating or blistering during any of the operations. In addition, such abearing blank is remarkably free from porosity and will require but aslight amount of rolling or pressing before the'tlnishing or machiningoperations necessary to complete the bearing. r A modification of thismethod may be employed with a certain type bearing whereby the properlyplatedsteel bearing member is placed in a die and the metal powderasabove is compressed upon all surfaces under a light'pressure not ex- .aperiod of 10 to 30 minutes in a reducing at- .mosphere in. a furnaceheld at a temperature not ceeding 7500 lbs. per sq. in.; the desiredpressure depending upon the density and other characteristics of thepowder. serves to density the metal powder layer to an extent wherebythe bearing blank with the powder layer upon it may be handled insubsequent operations. After this pressing operation, the

blank is sintered in a reducing atmosphere at a temperature of about1100 F. and cooled as before mentioned. It is then again compressed in asuitable die under a pressure of from 2500 lbs. per sq. in. to 20,000lbs; per sq. in. depending upon the thickness of the steel backing andthe metal powder layer. Final sintering then follows in a reducingatmosphere at a temperature of about 1700 F., whereby the metal powderlayer is bonded to the plated steel backing and the particles of powderare thoroughly united. Cooling is then eflected as before in a reducingatmosphere.

Another modification has been found practical with certain types ofbearing blanks, wherein the metal powder layer is spread loosely upon"the plated steel back and then sintered at a temperature not exceeding1700'. F. The blank is then cooled in a reducing atmosphere as before."

After the bearing blanks have been prepared as above, a pressingoperation may. or may not be necessary" depending upon the densitydesired in the finished bearing. In the case of theaverage bearing. suchas used in internal combustion engines, apressing operation is desirableand it has been found that a pressure of as high as 40 T. per sq. in.can be safely applied to the fingered metalsurface for the'purpose ofdensiflcation and for the purpose of sizing the blank to the desiredthickness. This operation may be a rolling operation, as shown in Figure7. We have' found that by our process this finalpressingoperationproduces a surface which may be used in many,applications without any machining. It of course is understood thatwhere the bearing blank has been made in strip "or other flat form,

a forming operation is required 'to produce thedesired shape, forexample, that of Figure 8.

One of the advantages of our method is that the metal powder may beapplied as-a loose layer on the steel back, and sinteredwithout lateralor longitudinal shrinkage and without the formation of shrinkage cracksin the sintered and slightly bonded to the plated steel, back, but notenough diffusion has taken place to cause appreciable shrinkage of thelayer. The pressing operation then so compacts the layerthat it can notshrink or crack in final sintering. In fact, a slight expansion is'noticeable in the final sinterlng operation.

The advantages of this process are particularly evident when thickbearing layers are desired and when sintering under pressure causesblistering andlead sweating. 4

Although we have described our process as using a platedlsteel backingmembenwe do not wish to confine ourselves to that alone. It is withinthe spirit of our invention to use any strong rigid material plated asdescribed or any copper base alloy such as argentiferous copper, bronze,brass or leaded bronze as' a backing member.

Having thus. described our invention, what we claim is:

This pressing operation surface. During our first or low temperaturesintering, the particlesof powder are slightly knit together vbooting-forming metallic material on the in non-compacted powdered formand then in a non-oxidizing atmosphere at a hire of from about 1100 to1700 F. in 1J1 to partially bond the particles of nqnpowder together andthe layer as a mic to the back. then pressing or rolling the a blankthus formed to compact the sintered layer eliminste-mbstantially allvoids therefrom,

y sintering said bearing blank in a nonatmosphere at a temperatur offrom t 1100 to 1700' 1". in order to complete of the particles togetherand the layer a whole to the back, and cooling in a nonpxiniisinga ere.q 2. The method of producing a bearing memfber which consistsessentially in placing a layer the bearing-taming metallic material innonpowdered form on the back and then mtering in a non-oxidizingatmosphere at a temperature of from about 1100 to 1700 F. in

1 'gpacted powder together and the layer as a whole v, M the back,cooling the blank thus formed ina finch-oxidising atmosphere. thenpressing or rolling said blank to compact the sintered layer to;eliminat e substantially all voids'theretrom, again faring saidbearinglblank in a non-oxidizing atmosphere at a temperature of about1700' F.

in order to complete bonding of the particles gender to partially bondthe particles of non-com-- together and the layer as a whole to theback, and cooling in a non-oxidizing atmosphere.

3. The method of producing a bearing member which consists essentiallyin applyinga coating of bonding metallic materialto a bearing blank,

placing a layer of the bearing-forming metallic sintered layer toeliminate'substantially all voids therefrom, again sintering saidbearing blank in a non-oxidizing atmosphere at a temperature of about1700" F. and cooling in a non-oxidizing atmosphere. v

4. A method according to claim 3 wherein the said bearing lblank issubjected to an additional pressing or rolling operation after thesecond sintering operation under a pressure not exceeding 40 tons persquare inch to density the hearing metal layer and size the blank to thedesired thickness.

ERNEST R. LDARBY. CARLOS M, HEATH.

